Robust Control based Energy Storage Stabilizers for Power Systems with Large Scale Renewables

This paper proposes robust control theory based stabilizers utilizing Energy Storage System (ESS) to improve the damping of power systems with high level Renewable Energy (RE) penetration. The proposed stabilizer can damp the electromechanical modes as well as the oscillation modes introduced by Converter Control Based Generators (CCBGs). A new weight-function for complementary-sensitivity function of system is proposed to improve robustness of the stabilizer. The weight function is developed by utilizing information from different operating points of the power system so as to improve the robustness. Controllability and observability indices are used to evaluate the effective input-output signals and the placement of ESS stabilizer. Detailed dynamic model of ESS representing energy storage, converter, PWM and filter dynamics is considered in the design procedure of the stabilizer. The physical limitations of ESS are considered in the stabilizer design by incorporating a new sensitivity function in to the objective function of H-infinity control. The IEEE-39 bus system is modified to represent 50-70% RE penetration level. Small-signal studies and time-domain simulations of the modified system are performed to verify the effectiveness of the proposed ESS stabilizer. Cost benefit analysis and sizing of the stabilizer falls out of the scope of this paper.